Design a cheaper CAN shield for chipKIT

[peplin]

It needs:

• Micro USB port
• Jumper pins or toggle switch to enable USB power
  • If not using USB power, drive A0 from micro-USB
• CAN headers
• CAN transceivers
• Port for RN-42 with a 6-pin header on it, bent 90 degrees
• Header pins to access UART RX/TX

[peplin]

I've designed a schematic on paper with the following:

• Micro-USB port, or optionally a spot for a 4 pin header to fit the SparkFun micro-USB breakout board if you can't do surface mount soldering
• A 5v regulator circuit using a switching DC/DC converter to make it more efficient
  • Protected from flipped 12v/gnd with a diode
• Split USB power from USB VBUS into 5v input on the chipKIT and A0, with a diode after going into A0 (so we can tell if it's actually connected to USB or just being powered from the vehicle)
• DB9 female connector on the edge
  • Uses non-standard pins to convert to an OBD-II connector so we can get CAN2-1 and CAN2-2 - if you used a standard cable it would still work, but only with CAN1
• A DPDT switch to select between CAN2-1 and CAN2-2 (This could be made controllable from the micro later on with a MOSFET, relay or analog switch IC but I'm keeping it simple for now)
• TJA1048T CAN transceiver, contains 2 transceivers so we can handle both channels with one IC
• A space for a surface mount RN-42, but also pins to add a header to connect a BlueSMiRF breakout board
  • The breakout board version won't support knowing if BT is connected or putting it into low power mode

Here's my sketch of the schematic, mostly so I can refer to it later when putting it into Upverter: